


My Monster (NSFW Chapters)

by AuroraDragon1983



Category: Undertale (Video Game)
Genre: Biting, Consensual Sex, Consensual Touching, F/M, Fingering, Fluff, Gentle Sex, Interspecies Relationship(s), Magical Genitals, Sensitive bones, Smut, bone touching, handjob, nuzzles, part of a different work
Language: English
Status: In-Progress
Published: 2019-07-07
Updated: 2019-09-14
Packaged: 2020-06-24 00:38:44
Rating: Mature
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 2
Words: 3,944
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/19712770
Author URL: https://archiveofourown.org/users/AuroraDragon1983/pseuds/AuroraDragon1983
Summary: Here you will find semi-canon nsfw chapters of my main ficMy Monsterwhich has a Teen rating.





	1. Sweet Spots

**Summary for the Chapter:**

> This takes place immediately after chapter 15. You and Sans decide to make each other feel good.

You finally give in to the temptation to run your fingers all over Sans's porcelain-like bones. Sans is breathing deeply in apparent relief. Apparently, he'd been nearly desperate to have you touch him. You pause your fingers periodically to feel his ribs expand and contract with each breath. He shivers and sighs as you gently stroke his lower ribs.

“didn't realise i was so sensitive there,” he says with shiver. “feels different than when i do it.”

“You sure you want me to keep going?” You ask carefully.

Sans smiles softly. “been wanting this for a while. it feels really good.” His hand has settled on your waist and squeezes gently, sending a shiver down your own spine.

Your fingers continue to trail across his ribs until they touch the front of his spine where his ribs connect. He sighs deeply and his eyelights fuzz out. His socket lids flutter closed and he arches his back slightly. “You like that?” You ask with a grin. He makes a weak sound of affirmation and nods. The sensation having your hand there is strange. It's like there is a slight electrical charge in the space and there is a slightly chilly tingle on your skin. This must be where his magic is concentrated.

Curious, you slowly inch your fingers upwards on his spine. Sans starts to squirm and his breathing becomes uneven. Suddenly, when your hand is about halfway into his ribcage, he freezes and takes a sharp inhale. You stop and pull your hand back. Sans's eyes are wide and the points of light are small. “Did I hurt you?” You ask worried.

He shakes his head. “no,” his voice is tight. “that's just a really sensitive spot. probably best to not touch it.”

“Ohh, okay,” you say in understanding. You imagine it might have felt like touching a raw nerve. “Do you want to stop or...”

He shakes his head again. “nah, it's fine,” he says with a soft smile. “i'm really enjoying this actually. learning about my own body and stuff.”

“Okay,” you say smiling back. “Is there somewhere specific you'd like me to touch?”

“um...” he looks down for a moment. “how about here?” He indicates with a slightly shaking phalanx the underside of his lowermost ribs. You follow his direction and run your fingertips along the underside of his lower ribs. He twitches and shivers again and you worry it was also uncomfortable, but he relaxes and a soft pleased groan emits from his throat. A blue flush creeps over his zygomatic. You then try stroking the outside and underside of one of the ribs rhythmically. Sans breathes an almost embarrassingly obvious moan of pleasure. His back arches again and his skull tilts backwards slightly. “oh stars...” he mumbles quietly as his eyes drift closed.

You try to position yourself so you can stroke both sides of his lower ribcage at once. Sans shudders and his breathing starts coming in huffs and his grip on your waist tightens, but not painfully so. His other hand is gripping the edge of the mattress tightly. He starts grunting and groaning as he squirms under you until his already glowing Soul gradually brightens. Sans's eyes open slightly and locks his gaze with yours. He looks delirious with bliss. He brings his free hand up and gently takes one of your hands from his ribs and slowly guides it down towards his lower spine. He guides you to stroke his lumbar vertebrae, particularly right where the spine connects to the back of the pelvis. The tingle of energy is quite warm in this part of his body.

He lets go of your hand and you continue to stroke the indicated vertebrae and the remaining lower rib at the same time. Sans's eyes go fuzzy again and continues to breathe heavily and make high-pitched whines. His spine arches further as the apparent waves of pleasure surge through his body as you keep stroking. This is really turning you on knowing you can please your bonefriend like this. You lean down and kiss his sternum. He sucks in a breath through his teeth and exhales a blissful moan.

You gently run your tongue over a few of Sans's ribs and you hear a laboured and breathy “haa... haa...” as he starts writhing in earnest under your ministrations. He seems completely lost in ecstasy as his ribs heave and he tries to move his pelvis in time with your stroking.

Right before you're sure he's about to pass out, his body seizes and shudders hard. His glowing Soul flares brightly as waves of blue magical light wash over Sans's bones. You pull your hands away from his more sensitive spots and gently stroke his sternum. After a moment, his body relaxes and he's panting like he just ran a mile. He manages to open his eyes and focus his eyelights. “holy sh-shit...” He stutters. “i didn't think i could feel that good.” He draws in a deep breath and exhales in a soft sigh.

You watch him for a moment as he recovers from what you assume is the skeleton equivalent of an orgasm. Suddenly, he perks up and looks at you with bright eyelights. “can i do that to you?” You're a bit taken aback by this. You certainly weren't expecting him to want to pleasure _you_ like that.

You blink a few times before answering. “Do you know how?” Your question is a bit vague, but Sans seems to know what you're getting at.

“theoretically,” he muses. “i, uh.. read a bit about.. erogenous zones and what feels good for women in general, but obviously everyone's different. you might have to help me there.” You nod absentmindedly. “besides,” he said with obvious embarrassment. “you'd be surprised how many of those graphic magazines end up in the trash.”

 _Oh... dirty magazines._ “Sans...” You protest.

“don't worry,” he says with a chuckle. “i know the difference between education and entertainment.” He sits up and looks at you with a curious smile as he waits for an answer.

It has been a long time since someone else has touched you in that fashion and you're already quite aroused in reaction to Sans's own pleasure. And to be honest, you're very curious to know what Sans's boney fingers would feel like on your skin. “Alright,” you say with a bright smile.

Sans moves so you can trade places with him. When he leans over you and gently places one hand on your hip, you shiver. His face lights up as he sees how sensitive you are now. He leans down and gives you a gentle nuzzle and then moves his face to nuzzle into the side of your neck. Damn, you _are_ sensitive. He's barely touched you and your heart is already racing. He moves his hand to creep under your shirt and gently trace his thumb over your own ribcage though your skin. He then moves his hand down a bit to squeeze very gently at the soft flesh of your abdomen which is one of your more sensitive areas. You shudder and exhale a puff of breath. You hear Sans chuckle slightly at discovering one of your sweet spots.

He trails his fingers upwards and over your bra. “is this okay?” He whispers in your ear.

“Yeah,” you say softly. “I can take it off...”

“if you want to,” he says calmly as he sits back on his heels. You sit up and manoeuvre your shirt and bra off. Sans looks at you in awe as you lay back down, now bare-chested. He reaches cautiously towards one of your breasts and looks at you for permission. You nod and smile and he gently palms one of your breasts and massages slowly. “dang, that's soft,” he says in admiration. He gently teases the nipple between his thumb and forefinger and smiles when you shiver at the sensation. Despite his fingers being hard, it doesn't hurt at all. Unexpectedly, he leans down and puts his mouth over your other nipple and teases it with his magical tongue. The tingling sensation is surprisingly intense and your whole body shudders and you instinctively put a hand on the back of his skull and stroke it.

He continues his oral ministrations as his other hand leaves your breast and gently drags over your midriff and abdomen again. The tips of his distals dip just under your waistband he lifts his head momentarily to ask, “can i touch you here?”

You're so aroused at this point, you barely have to think about it. “Please,” you whisper. He smiles sweetly and leans up to kiss you. His other hand continues to tease one of your nipples as his phalanges slip under your waistband and under your panties to touch your clitoris. You're pretty soaked now and you can tell that Sans can feel it. He nuzzles your neck again as his fingers slip between your folds and rub your clit gently. He seems to be putting his 'research' to use as he rubs the bundle of nerves firmly and rhythmically in a similar fashion that you had done to him. It seems to be doing the trick as the sensation is felt though your whole body. Waves of heat wash over your skin as he rubs at just the right spot to make you squirm and get even more aroused.

After a few blissful moments of you getting closer and closer to climaxing, Sans pauses his rubbing to whisper in your ear. “can i go inside you?”

Those words alone make your already racing heart skip a beat. You manage to say the word “yes” and he pulls back slightly so he can look at your face. He watches you with loving curiosity to see your facial expressions as his fingers slip downwards and trace the flesh around your entrance.

He slips one phalanx inside your core first which immediately causes you to clench at the intrusion, causing Sans's eyesockets to widen, but you quickly relax as he starts massaging your inner walls. He then, carefully inserts a second phalanx and pushes them deep inside you. You clench again as your body shudders with pleasure. You hear him breathe the words “so soft” as he presses his fingers into the warm flesh of your core. You start squirming as he slowly thrusts his fingers into you and periodically curls them to rub against your pubic bone. Your hands find themselves clinging to various points of his spine. Sans grins at you as you both become aware of the shift in dynamic. You had pleasured him until he was putty in your hands, and now he's returning the favour.

As he curls his fingers to thrust into your soaked core, he rubs his metacarpals against your clit, sending waves of pleasure throughout your body. You instinctively spread your thighs further apart so Sans can get further inside. He then inserts a third finger and starts thrusting vigorously. He has yet to break eye-contact with you and has been watching your bliss-filled face as he gradually increases the intensity of his ministrations. The exquisite stretching of your inner walls and the slightly rough texture of his knuckles causes them to flutter and twitch.

Eventually, you can't keep eye-contact anymore as you, too, get lost in pleasure as he thrusts into your core and rubs your clit relentlessly. Your blissful moaning indicates to Sans that he's doing something right. “come on,” he whispers gently. “come for me.” He times his movements just right and a flush of heat surges through your body. Your back arches and your hips rise up to meet Sans's thrusts and he pushes deeply one last time as he drinks in the sensation of your inner walls clenching and unclenching against his phalanges.

He moves his other hand over to rest on your sternum and feel your pounding heart. Slowly you relax and your bent knees flop lazily to the sides. Sans carefully withdraws his fingers from inside you and from your pants. He looks curiously at the wetness now coating his phalanges. “that felt good, right?” He grins a bit smugly and you barely register what he said. Instead of answering, you just start laughing and you reach up and pull him down and embrace him. You tilt your head to reach his neck vertebrae and kiss them gently. You feel him shiver and sigh as he relaxes his weight onto your body. “That was really good,” you whisper as you nuzzle the side of his skull.

“glad i could be of service,” he says softly. You lay together for several minutes before you reluctantly get up to properly get ready for bed.


	2. Closer

**Summary for the Chapter:**

> Takes place right after chapter 24. Sans claims you as his Mate in a more physical sense.

After several minutes of embracing each other under the glittering stones on the ceiling, Sans starts to fidget. He pulls back from you a bit and scratches the back of his neck vertebrae; clearly trying to think of something to say. Eventually, he looks at you with a slight flush of blue on his face. "yn? there's something i wanted to try doing with you. not something i've ever done before so i might need your help getting it right, cause it's more of a human thing."

You give Sans a soft but curious smile. "What's that, Sans?"

He takes a breath. "i wanna-" takes another breath. "i wanna make love with you... i think that's what it's called."

Your brain fizzles for second. For some reason that sounds weird being said by him, but you can't help but smile wider at the sentiment. "You mean like we did before?" You blush at the memory.

He shakes his head nervously. "nah. i, uh, made something... out of magic that i wanted to use." His hand trails absentmindedly to the front of his pelvis. You flush when you realize what he's talking about.

You sit forward and look at him curiously. "You made... genitals?" He nods shyly.

"i'm pretty new to havin' it, so i'm not sure how sensitive it's s'posed to be. i don't think my boney fingers are really suited for testing it, but maybe if you touched it?"

You can't help but look curiously at whatever Sans is handling in his shorts. "Would you like me to?"

He nods again. "yeah, i wanna try something new to me and be really close to you and make us feel good."

You chuckle softly and smile sweetly at him. "That's what lovemaking is, babe." Sans's blush spreads a bit more and he looks up at you shyly. "Show me what you'd like me to do."

Sans shuffles a bit closer and you position your legs so they are surrounding him while he sits in front of you on his knees. He looks up at you for reassurance before he takes the waistband of his shorts and pulls it down and under his pubic bone. What you see holds your gaze for several seconds. A translucent glowing blue phallus resembling an erect human penis is attached to his pubis. The size is not unsatisfactory. You reach for it tentatively and you look up at Sans to make sure it's okay. He nods slowly and you very gently trace a finger over the topside of the glowing appendage. You can feel an electric heat radiating from it and Sans twitches at your touch. He leans forward and buries his face in the side of your neck and rests a hand on your leg.

"You okay?" He nods. "I can keep touching?" Nods again. You gently stroke the topside of the magical phallus with your palm. Sans is breathing deeply as he adjusts the sensitivity so he isn't overwhelmed by the slightest of touches. You wrap you fingers and thumb around the base of his penis and start stroking slowly. Sans shudders and his fingers on your leg flex and squeeze. You move a bit faster, but keep your grip gentle and Sans's warm breath puffs against your neck. You notice something you didn't the last time you were intimate with Sans; possibly because he hadn't used his magic in this fashion before. His magic has a scent. It smells like rain or melted snow. You think the right word is 'petrichor'.

After a few more minutes of getting Sans hot and bothered, he draws in a deep breath and leans back with unfocused eyes and flushed cheekbones. He carefully pulls your shirt up and over your head and brings his hand up and gently presses against your shoulder; nudging you to lie down. You let go of his conjured phallus and lie on your back. You and Sans manoeuvre your pants off and he gently lays himself on top of you. He snakes an arm under your shoulder blades to cradle the back of your neck while nuzzling and kissing where your neck meets your shoulder. His ribs press against your breasts and his pelvis presses against yours. He starts rubbing his cock against your now slick outer folds.

"you'll tell me if this is uncomfortable, right?" He whispers in your ear.

“Yeah," you say softly as you rub the back of his ribs.

He takes a few seconds trying angle his hips to line his cock with your entrance, but has to use his hand to get it in place. Gently, he presses the tip against you until it slips inside. The heat and what feels like a weak electrical current immediately makes your walls clench and Sans grunts at being squeezed.

He pants a few breaths. "you okay?" He asks with a tremble.

"Yeah," you reply, breathily. “You?”

“yeah,” he says nodding. “i can keep going?”

“Mm-hm,” you mumble needily. Sans steadies himself on his knees and braces himself with his grip around your back as he moves his pelvis to ease himself deeper inside you. You try your darnedest to relax, but the hot energy radiated by his cock causes your inner walls to twitch and squeeze around it. Sans pauses his entry periodically to make sure he isn’t hurting you.

After a few agonizingly delicious moments of increasing pressure within you, his pubic bone meets your entrance and you can feel the tip of his cock press against your cervix. Sans takes a few breaths and his grip around your shoulders tightens. He pulls himself sharply to secure himself as deeply inside you as he can get. Your inner walls clench tightly and it almost sends you over the edge to be fully penetrated and filled like this. The energy emitted by his conjured phallus seems to make your entire nether-regions vibrate. You’re not sure if the pulsing you feel where your bodies are connected is coming from your own racing heart or from him.

Sans pulls back to look at your face and he has a look of shock on his flushed face. It's like he can’t believe he is doing this with you and that you could both feel so good at the same time. You can barely believe it, either. It's like a strange fantasy come to life that you could make love with Sans. You feel his breath against your own mouth as you feel his ribs expanding and contracting against your own chest. He leans down and nuzzles and kisses you while his pelvis shifts slightly to rub against your entrance and test a few different angles. He pulls out about half way before pushing back in smoothly. He groans softly at the sensation and you shift your own hips to meet his thrust.

He secures his hand on the back of your neck and pulls out again. This time he starts thrusting in earnest. It starts out slow and it takes a few thrusts and you occasionally grasp his hips to help him settle on a satisfactory angle that he can sustain and that feels good for both of you. He manages to confirm now and then that you feel good and you’re almost too lost in the pleasure of his gentle but firm thrusts to respond clearly. It feels like he’s massaging you from the inside. He isn’t thrusting with a great amount of vigour, but you can tell he’s making each thrust count; getting it right before getting too confident.

After several minutes of bliss, Sans shifts his weight slightly and increases the speed of his thrusts to an almost clockwork pace. His expression slowly shifts from fascinated curiosity to increasing confidence in his motions. His ribs rubbing against your breasts and the electric heat surging through your body like lightning pulls blissful moans and words of encouragement from your lips. Sans’s spine curls and flexes with each thrust as his breaths come out in huffs and grunts from the exertion. You can barely control where your hands go, but one of them ends up curled around the base of his spine. You start thumbing the sensitive spot you know of and Sans noticeably twitches and a deep rumbling emits from his chest.

You start to feel a familiar warm tingling against your stomach and while you’re in no position to look, you imagine Sans had formed ethereal abdominal muscles to aid him in his thrusting as his pelvis starts grinding vigorously into your core. The tingling makes contact with your clit, which brings you to the edge of ecstasy. Somehow, he manages to form words between breaths. “y’know, _(huff)_ all this time _(haa)_ i had your magic inside me. _(huff)_ now that i _(unf)_ have my magic inside you, _(puff)_ it feels so good _(huff)_ i can’t stand it.”

Suddenly, you feel Sans’s teeth clamp down on your shoulder. It isn’t painful, but the pressure is enough to send you spasming through your whole body. You hear Sans grunting through his teeth at being squeezed by your inner walls. He must have been waiting for you reach your climax, because his arms tighten around you and you feel waves of magical energy wash over his bones; under your fingers. He stops thrusting, but his seizing body pushes his hot magical cock deeply inside your core and stretches you lengthwise.

Slowly, Sans’s body relaxes. He releases your shoulder from his teeth and sets his full weight onto your body. You keep your arms around his ribs as they heave with each breath. The magical cock that is lodged inside you slowly dissipates now that Sans is too exhausted to maintain it. He withdraws his arms from under your shoulders and tries to push himself up but fails and just lays on top of you like you’re a body pillow; which you don’t mind at all. A tiny voice in the back of your mind tried to tell you that being sexually active with a non-human creature is wrong, which is true... But this is different; very different. Monsters are not animals. They may not be human, but they **are** people. In this moment, you realize you’ve never felt as sexually and emotionally fulfilled as you do with Sans. You know he loves you and he knows that you love him and you both made each other feel wonderful because of it.

You lay together for several minutes just holding each other and breathing together until you actually start to get cold. You both decide to head back to his house and as a show not wanting to move, he simply holds onto you and the ground is suddenly replaced with a mattress. You can’t see anything in the darkness, but you just assume he brought your clothes along. You pull the wrinkled blanket over you both and finally doze off.


End file.
